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Modern engines rely more and more on the engine oil to serve increasingly complex hydraulic functions such as, for example, controlling cylinder deactivation - a means of significantly increasing fuel efficiency. However, the success of hydraulic methods of activating mechanical responses in engines (or other devices) is dependent on the degree of incompressibility of the hydraulic fluid. As a consequence, those engine oil properties that impart susceptibility to foam formation in areas of hydraulic operations of the engine are detrimental to the engine's performance and durability. This paper is an initial study of aeration, air entrainment, and air release under pressure decrease using a simple bench test. The preliminary information reported suggests the potential application of the instrumental approach developed to measure the rate of foam formation from the air entrained in engine oils and the resistance of such foam to collapse.